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Infectious disease > Rickettsia > Flashcards

Rickettsia Flashcards

1
Q

What causes rickettsia

A

Rickettsiaceae

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2
Q

What do rickettsia genus cause

A

Spotted fever
Typhus fever
Scrub typus

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3
Q

Causes of spotted fever

A

Rickettsia rickettsii (rocky mountain) - orth america
Rickettsia akrai (boutonneuse fever)
Rickettsia sibricia , australis felis - flea, japnoica, africae
African tick bite fever

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4
Q

Typhus group of rickettsiae causative organsims

A

Rickettsia prowazekii - epidemic typhus, recrudescent typhus, sporadic typhus
Rickettsia typhi - murine typhus (endemic typhus)

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5
Q

Scrub typhus group causative organisms

A

Rickettsia tsutsuganmushi

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6
Q

What is scrub typhus

A

Acute febrile infectious disease caused by orientia tsutsugamushi

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7
Q

Symptoms of rickettsia

A

Eschar
Regional lymphadenopathy
Fever
Maculopapular rash
Leukopenia

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8
Q

What is o.tsutsugamushi sensitive to

A

Chloramphenicol and tetracycline

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9
Q

Source of infection and transmission of rickettsia

A

Rat -> trombiculid mites
Transmitted to humans by arthropods - ticks, mice, louse, flease
Larva of trombiculid mite
Spread by haematogenous or lymphatics

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10
Q

Immunity to serotypes once have rickettsia

A

Only to that serotype - no protection from others

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11
Q

What is the tsutsugamushi traingale

A

Geographical area where ecposed to rickettsia -
Northern japan and far eastern russia
to northern australia to pakistan and afghanistan
Jungle, scrub and grassland

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12
Q

Seasonal peaks in north vs sotuh

A

South - may to cotober with maximal peak june to july
North - septmeber to december w maximal peak in october

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13
Q

Features of o.tsutsugamushi bacteria

A

Obligate intracellular parasites
Gram negative coccobacilli
RNA and DNA (binary fission_
Stains red on giemsa or gimenez stain

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14
Q

What colour does o.tsutsugamushi stain on giemsa or gimenez stian

A

Red

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15
Q

Pathogenesis of rickettsia

A

Maculopapular rash, eschar, ulcer
Enlargement of local ly,ph node -> blood
General symptoms sepsis -> generalised hyperaemia, systemic lymphadenopath

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16
Q

INcubation period of rickettsia

A

4-21 days

17
Q

Presentation of firs week of ricketttsia

A

Sudden onset of fecer - systemic toxic symptoms

18
Q

2nd week vs 3rd week of rickettsia

A

3rd week - Worse, complications, 4th week convalesce

19
Q

What is eschar

A

Ulcer surrounded by red arcola often overed by dark scab

20
Q

Most common areas for eschar location

A

Axillary fossa, inguinal region, perianal region, scortum, buttocks, thigh

21
Q

What is most specific manifestation of scrub typhus

A

Eschar

22
Q

Specific features of rickettsia

A

Eschar
Maculopapular rases (end of first week, chest, abdo, trunk, upper or lower limbs)
Local lymphadenopathy

23
Q

Haematology/biochemical markers of rickettsia

A

Leukopenia
Normal WCC
Elevated w complications
Injury of liver function, CRP

24
Q

What test for rickettsia

A

weil-felix test (esp in healthcare restricted settings)

25
Q

How early can weil felix be psotivie

A

4th day after onset

26
Q

What is diagnostic from weil-felix test

A

> 1:160 or increase 4 fold during course
Poor specialisation

27
Q

What is gold standard tests for rickettsia

A

Indirect fluroescent antibody - IFA -
IIP - indirect immunosperoxidase test

28
Q

When can IFA for rickettsia be postive from

A

positive from end of first week
Lasts for years

29
Q

Pathogenic examination for rickettsia

A

Culture - use in mouse
Spleen and liver biopsy - stain with giemsa
PCR - orientia DNA
Not routinely available

30
Q

Early course pathology of rickettsia

A

Perivascular lymphohistiocytic infiltrate and extravasated erythrocytes and dermal oedema
Dermal and epidermal necoriss later
positive r.rickettsiae imunohistochemical stain

31
Q

Criteria for diagnosis of rickettsia

A

Visit endemic area last 3 weeks - work ,camp, grass sit
Clinical manifestation
Lab exam - weil feliz reaction

32
Q

Differential diangoses rickettsia

A

Epidemic typhus - winter and spring louse bite, weil-felix and OX19 +
Typhus
Leptospirosis
Dengue
Kawasaki
Malaria
MEasles
Meningococcal
Rubella
Strep A
Syphilis
Toxic shock syndrome
Vasculitis, thrombophlebitis

33
Q

Typhus features

A

slow onset fever. Confusion, bradycardia, digestive symtpoms, rose rash, no eschar, widal test positive
+ culutre of typhus bacilus positive

34
Q

Leptospirosis how differntiate

A

Calf muscle tenderness
Microscopic haematuria

35
Q

General treatment

A

IV fluids supportive
Intensive nursing care and prevent complication
Sensitive antibitics - mortality drastically reduced

36
Q

Treatment regimes for rickettsia

A

Chloramphenicol - 2g/day (25mg/kg child)
Doxycycline - 0.2g/day adult (tetracycline alt)
Azithromycin 500mg daily
Roxithromycin - 0.6g/day adult - 2-3mg/kg/day child ESP in child useful

37
Q

Treatment if resistnat rickettsia strain

A

Combination therapy doxycycline and rifampacin
Azithromycin

Infectious disease (37 decks)

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